Telephone system



, TELEPHONE SYSTEM Filed March 27, 1955 OR W ATTORNEY Patented May 26, 1936 UNITED STATES PATENT OFFICE TELEPHONE SYSTEM Horace W. Ulrich, Newark, N. J., assignor. to Bell Telephone Laboratories, York, N. Y., acorporation Application March 27, 1935, Serial No. 13,205

6 Claims.

ing the same linenumber but widely scattered. as to location. as; for example, any multipartyline such as four-partyselective; two-party semiselective or where so-called' secretarial and physician call bureauserviceis given in the-larger cities. Further, it is quite common forv professional men who have business lines in; their-ffices, to have extensions of' these, lines located at their residence which may be at some distance from their ofii'ce and frequently in another exchange area.

In all these cases and particularly where the wires arecontained in cables, speechtransmission over the line is frequently impaired due to. the

combined capacity of the bridged. pairs of wires- An object of the present invention is to eliminate suchfbridged tap'losses in caseswhere two.

or more pairs of:'wires are connected: together in multiple.

A feature-off the invention whereby the foregoing object is attained residesin disconnecting.

all the bridged pairs from the main line except the pairs connected: to stations at which receivers have been removed from the hook.

Inv this connection it may be observed that a great majority of 'calls only one-station on the line will have its receiver off the hook and, therefore, a circuit free of bridgediimpedance will. extend from the switchboard tothe station in use. However, as referred to above, in case of a revertive call, that is, a call from one'station to another station connected to the same line, but on a different bridged pair, the removal of the receiver at the second, orcalled station, will be efiective to connect its loop or-pair acrossthe line in parallel with the calling'station: pair.

The arrangement of the present invention differs from the-arrangement disclosedinthe patent to Barrows, et' al., 1,227,735, dated May 29,.

1917, in this feature, i. e. means forpermitting a second station to connect to the main line merely by the removal of its receiver, which was not-possible in the Barrowsarrangement.

'I'heinvention willbeunderstood f'rom the fol Incorporated,. New of New York lowing description when read in connection-with the accompanying drawing which shows a plurality of bridged pairs connected to a common line circuit terminating; a telephone switchboard and arranged in accordance with the present invention;

Referring to the drawing, there are'shown four subscribers" lines or loops arranged according to this invention: for four-party selective ringing. Lines I; 2, 3 and 4 terminate at the respectively in substations 5, 6, 1 and 8; at only one of which has the usual circuit arrangement been shown in detail, These lines are terminated at their inward end'ata central office CO. One

of the conductors. of each line passes through thewindings of respective relays 9, H); II and I2, and then: throughrthe-normally closed lower con.- tacts, of relays: I23, I4", l5 and It, respectively. Each of the other'conductors of said lines passes through the upper normally'closed contacts of relays. l3; l4, l5 and I6, respectively. After passing through said'relaycontacts all four lines are multipled together and connectedto jack I7, with which. is associated the usualline relay l8, line lamp [9; and cut-01f relay 2|]. A- detailed description: of'the operationof'the circuit arrangement of. the drawing willnow be given;

Let it: be assumed: that the subscriber 5 0i line I desires to initiate acall to some line other than one of the associated lines 2, 3 and 4. On removing the receiver 2| from the associated switchhook 42' a: circuit is closed through the windingsof line relay l8; which may be traced from battery through the right-hand winding'of'relay l8, outer contacts of relay 20, over conductors 22 and 28; lower normally closed contacts of relay l3, winding of relay 9-, including non-inductive resistance 24', over ring conductor of line I', through transmitter 25 of subscribers station 5', switchhook. contacts 26, left-handwinding of induction 40 coil 21', overtip conductor of line I, through upper normally closed contacts of relay l3 over conductors.3land 23, inner contacts of relay 20', to ground through the left-hand winding of relaylBL Relay lfl operates andclosesan obvious circuit through. line lamp l9, which lights. In responseto the lighted lamp, the answering operator: inserts plug 30' of cord' circuit 29 into jack I l. C'ordicircuit 29 is of the usual common-battery type and is shown onlyin abbreviated'form. The insertion of plug 30 closesa circuit for-operating cut-ofi relayZll', which may be traced from ground through the winding of relay 20, sleeve contactsof'jack I]: andplug 30 to battery. Relay Min-operating: disconnects from conductors outward end,

22 and 23, the windings of relay I8, which releases and opens the circuit of lamp I9, which is extinguished. When the plug 30 of cord circuit 29 was inserted in jack I'I, battery 32 was connected over the tip and ring contacts to conductors BI and 28, respectively, and thence was extended over the circuit previously traced in describing the operation of relay I8. Relay 9 now operates and connects ground to both winding terminals of relay I3 and to conductor 33 over obvious circuit paths. Relay I3 is therefore short-circuited and does not operate, thereby maintaining the continuity of the conversational circuit between the answering operator and the calling subscriber at station 5. The ground on conductor 33 connected thereto by the operation of relay 9, however, causes the operation of relays I4, I5 and I6, through circuits including resistances 35, 35 and 31, respectively, thereby disconnecting lines 2, 3 and 4 from their connection with conductors 22 and 23. According to a feature of this invention this disconnection of lines 2, 3 and 4 removes the bridged transmission loss which would result due to the electrostatic capacity of said lines 2, 3 and 4. After receiving the number of the desired line the operator now completes, in the usual manner, with the calling end (not shown) of cord circuit 29, the connection to the desired line, which, as hereinbefore assumed is not one of the associated four-party line branches.

When relays I4, I5 and I6 operated they also connected the tip conductors of lines 2, 3 and 4 directly to conductor 38, and the ring conductors of said lines to conductor 39, through the windings of relays I9, II and I2, respectively. Let it be assumed now that while subscriber 5 is conversing over the connection hereinbefore described, one of the other subscribers, subscriber 6 for example, desires also to call the central office. On removing his receiver from the switchhook, a circuit is closed for operating the associated relay I 9, through a circuit that may be traced from battery through resistance 40, over conductor 39, through lower operated contacts of relay I4, winding of relay I9, over ring conductor of line 2, through substation 6, over tip conductor of line 2, upper operated contacts of relay I4, over conductor 38, through resistance M to ground. Relay I9 operates and connects ground to both winding terminals of relay I4, thereby short-circuiting said relay I4 and causing its release. When relay I4 releases, it reestablishes the normal connection of line 2 to conductors 22 and 23, and relay I9 holds on the battery of cord circuit 29, connected through the contacts of plug 39 and jack IT to conductors 22 and 23. Relay I4 is provided with so-called continuity contacts in order that the transfer of the conductors of line 2 from connection with conductors 38 and 39 to connection with the conductors 22 and 23 may be made without interrupting the operating circuit of relay I0. In the case of subscribers I and 8 there would be a similar circuit action if either of these should attempt to call when line I is busy'. After line 2, is thus reconnected to conductors 22 and 23, the subscriber 6 is enabled to determine that the line is busy and accordingly restores his receiver to the switch-. hook causing the release of associated relay I9, and the reoperation of relay I4, from ground on conductor 33, connected by the contacts of relay 9 of line I, which by previous assumption, is

'busy. .The reoperation of relay I4, accordingly disconnects line 2, and again removes the bridged.

transmission loss due to the connection of this line. After the subscriber 5 hangs up receiver 2|, relay 9 releases, releasing also relays I4, I5 and I3. After the operator receives the usual disconnect signal (not shown), plug 29 is removed from jack I'I, releasing cut-off relay 20. All apparatus is now restored to normal, ready for another call.

Another operating condition of the invention will now be described. Let it be assumed that one of the stations 6, I or 8 desires to call station 5. For purpose of description assume that the calling station is station 6. When the receiver at station 6 is removed from the switchhook the relays of associated line 2 function in the same manner as the corresponding relays of line I, as hereinbefore described in connection with the call originated at station 5. After 7 line relay I8 operates, lighting line lamp I9, the

operator inserts the plug 30 of cord circuit 29 into jack I'I, causing the operation of cut-off relay 20, and the disconnection of the windings of line relay I8, all as hereinbefore described. The operator now ascertaining that the call is for station 5, a so-called revertive connection, i. e., for a station with the same line number, will request station 6 to hang up for a moment while station 5 is being called. The operator now connects grounded ringing current by a ringing key (not shown) to the conductors of cord circuit 29. This causes the operation of relay 43 and ringer 45, as will be evident from the hereinafter given description. Assuming that the non-grounded terminal of the ringing current source (not shown) which is of the proper polarity to ring ringer 45 is connected to the tip conductor of cord circuit 39, the circuit proceeds through the tip contacts of plug 30 and jack I'I, over conductor 3|, through upper normally closed contacts of relay I3, over tip conductor of line I, through left-hand winding of induction coil 21, winding of relay 43, condenser 44, over ring conductor of line I, through winding of relay 9, including resistance 24, lower normally closed contacts of relay I3, over conductor 28, through ring contacts of jack I1 and plug 30, and ring conductor of cord circuit 29 to the other or grounded terminal of said source of ringing current. Relay 43 in operating connects the winding of ringer 45 to the tip conductor of line I. The ringing current potential on said tip conductor causes a flow of ringing current through the winding of ringer 45 to ground and thence by ground to the grounded terminal of said ringing current source at the central office C'O. Ringer 45 is now actuated, as it is poled to respond to the polarity of the ringing current which is now being applied, and only to said polarity. In response to the ring of ringer 45, subscriber 5 removes his receiver from the switchhook. When calling subscriber 6 also again removes his receiver from the switchhook, after having waited for the operator to ring, the conversational connection is completed due to operation of series relay I0 which short-circuits relay I4, which relay is now operated due to the ground connected to conductor 33 at the lower contacts of relay 9. When relay I4 is short-clrcuited it releases, as previously explained, and reconnects the line 2 to the common line conductors 22, 23. Transmitter current for both stations is now supplied by cord circuit battery 32. During the ringing interval, although ringing current passes through the windings of relays 9, III, II and I2, these relays,

however, do not operate at this time, since they are designed not to operate on the alternating ringing current that passes over their associated lines I, 2, 3 and 4, respectively.

The descriptions hereinbefore given were for calls originating at one of the four stations, first, for a non-associated station, that is for a nonrevertive call; secondly for an associated fourparty station, that is for a revertive call. The operation of the invention will now be described for an incoming call from a non-associated station directed to one of the stations 5, 6, 1 or 8. For descriptive purposes let it be assumed that is the called station. On receiving a call for station 5 of line I the operator having access to jack I! will plug into jack I! with either the calling plug of a cord circuit or of a trunk circuit, each not shown. With the proper polarity of grounded ringing current applied to the tip conductor and ground to the ring conductor of line I, ringing current is transmitted over line I so as to operate ringer 45 of station 5, in the manner described hereinbefore in connection with a revertive call. When the receiver 2| is removed from the switchhook all apparatus functions as hereinbefore described in connection with an originating call.

The invention has been described in connection with its application to a four-party selective line system. It is to be understood, however, that it is also applicable to other party line systems; for example, it can be applied to a fourparty semi-selective system, or to a multiparty non-selective arrangement of lines, where the individual subscribers are called by a system of code ringing. It may also be used for call bureau service. In this case the line to the subscriber, and the line to the call bureau may be widely separated and may be arranged according to this invention so that when either line is busy, this causes the disconnection of the other line, if idle, thereby avoiding the bridged transmission loss due to the idle line. Still other arrangements of a similar nature will readily occur to those skilled in the art.

What is claimed is:

1. In a common battery telephone system, a plurality of subscribers stations, a line for each station, a common line normally connected to all said station lines in multiple, cut-off means individual to each station line for disconnecting its station line from the common line, other individual means in each station line responsive to currents flowing therein to disable its companion cut-01f means and actuate all others, an auxiliary circuit including a source of direct current, and means for connecting said auxiliary circuit to all station lines whose cut-oil relays are operated.

2. In a telephone system, a subscribers line, a plurality of subscribers stations, a branch line for each sub-station, an individual cut-off relay for connecting and disconnecting each branch line to and from the subscribers line, a relay in each branch line and controlled by the associated subscribers station equipment, a common energizing circuit for all cut-01f relays closed by the operation of any one branch line relay, circuit means controlled by each branch line relay for short-circuiting its associated cut-01f relay, and an auxiliary circuit including a source of current adapted to be connected to each branch line in substitution for the subscribers line when the individual cut-ofi relay operates.

3. In a telephone system, a central station, a subscribers line, a plurality of subscribers stations, a branch line for each subscribers station, a cut-off relay for connecting and disconnecting each branch line to and from the subscribers line, an individual relay for each branch line having an energizing winding in series therewith, a common energizing circuit for all cut-off relays including the front contact of any one of the branch line relays, individual circuit connections for short-circuiting each cut-off relay, said circuit connections including a front contact of its corresponding branch line relay, and a source of direct current adapted to be connected to each branch line by the operation of the corresponding cut-oil relay.

4. In a telephone system, a central station, a common battery subscribers line extending therefrom to a connecting point, a plurality of subscribers stations, a branch line extending from each subscribers station to said connecting point, a cut-off relay for each branch line located at the connecting point and adapted to normally connect the branch line to the subscribers line in multiple. and when operated to disconnect said branch line therefrom, a series relay in each branch line adapted to be operated when its associated substation receiver is removed from the hook and an energizing circuit for all of said outoff relays adapted to be closed by the operation of any one of said series relays, circuit means controlled by the operation of each series relay for short-circuiting its corresponding cut-off relay, and an auxiliary circuit including a source of current adapted to be connected to each branch line in response to the operation of its cut-01f relay.

5. In a common battery telephone system, a plurality of lines, a common line normally connected to all of said station lines in multiple, cutoff means individual to each station line for disconnecting its respective line from the common line, other individual means in each station line responsive tocurrent flowing therein to disable the companion cut-ofi" means and actuate all other, an auxiliary circuit including a source of direct current, and means for connecting said auxiliary circuit to all station lines Whose cutoff relays are operated.

6. In a telephone system, a plurality of branch subscribers station lines, a common line normally connected to all said branch lines in multiple, means responsive to the closure of any branch line at a subscribers station for disconnecting all the other branch lines from the common line to the exclusion of the closed branch line, and other means thereafter automatically responsive to closure of any one of said disconnected branch lines for reconnecting it to the common line to the exclusion of the other disconnected lines.

HORACE W. ULRICH. 

